The present invention relates to a device for measuring the distance between two points and, more particularly, a sensor capable of measuring the distance by magnetic field means.
Various sensors have been developed along with the progress of micro-computers. Among these sensors are included the one for measuring the distance between two points.
The distance is conventionally measured by the angle of a rotary encoder arranged, as a distance-measuring sensor, so it is turned at a point where two sides of a triangle intersect. Assuming that the length of one side of the triangle is l, the distance can be obtained from 2 l sin .theta./2 wherein .theta. represents the angle formed by two sides of the triangle.
The distance is also measured using the capacitance of electrodes arranged at both ends of the distance to be measured. Assuming that the area of each electrode is s and that the distance between them is d, the capacity c is equal to .epsilon.s/d, where .epsilon. represents the dielectric constant of a dielectric present between the electrodes. The distance d can be obtained from this equation c=.epsilon.s/d.
The rotary encoder is limited in use because it specifies two points mechanically. The capacitance structure is likely to be influenced by ambient circumstances, thus making errors because of humidity, position of measuring person and so on.